JPH043536B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a still camera and a video camera with a built-in autofocus device, and more specifically to a camera that adjusts the limit position of the photographing lens according to the brightness of the subject so that the limit position is approximately at the hyperfocal distance. This is about an autofocus camera that has been changed.

Auto focus cameras have a built-in distance measuring device that detects the shooting distance to the subject, and the output signal from this distance measuring device is used to set the photographing lens between a short distance position and a limit position. . In particular, with still cameras, when the camera is released, the photographing lens is moved from a close position to the limit position, and while the photographic lens is moving, the stopper is driven by the output signal of the range finder, and the photographing lens is moved to the focused position. There are many methods that require setting.

Generally, a position where the photographing lens is focused at the hyperfocal distance of an open aperture (hereinafter referred to as the hyperfocal position) is used as a limit position for regulating the maximum movement of the photographic lens. This hyperfocal position means that if you set the photographic lens at this position, you will be able to get good focus all the way to infinity.
The feature is that the hyperfocal distance becomes shorter as the aperture value increases.

Taking these features into consideration, the camera described in Japanese Patent Publication No. 51-14891 is designed to set the above-mentioned limit position to a pan-focal position corresponding to the aperture diameter depending on the brightness of the subject. However, this camera has a configuration in which a limit position is set for each aperture diameter determined by the brightness of the subject, resulting in a complicated structure and high cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved autofocus camera that can obtain clear images over a wide range from near distance to infinity.

In the device of the present invention, when the subject brightness is below a first level, the aperture is kept constant and only the shutter speed changes, so that the limit position is almost the hyperfocal position, and when the subject brightness is below the first level, the aperture and shutter speed are changed. The limit position is changed in accordance with the characteristics of the program shutter which change in both of the above.

Embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, a photometric circuit 1 includes a light receiving element 2 that converts incident light into an electrical signal, outputs a signal corresponding to the brightness of a subject, and sends the signal to comparators 3 and 4 and a program shutter control circuit 5. The threshold levels of these comparators 3 and 4 are determined according to the aperture characteristics of the program shutter control circuit 5. In this embodiment, the comparator 3 has a subject brightness BV of 6.5.
(When using ISO100 film, the light value LV
11.5) Outputs a high level (hereinafter referred to as "H") signal in the following cases. The comparator 4 outputs an "H" signal when the subject brightness BV is 9.5 or more (light value LV is 14.5 when using film of ISO 100). The output signals of these comparators 3 and 4 are input to the NOR circuit 6, and the subject brightness BV is
When it is in the range of 6.5 to 9.5 (LV11.5 to 14.5), the NOR circuit 6 outputs an "H" signal.

The matrix circuit 7 is for generating different code signals according to the input signals a to c, and for example, a row line grounded through a resistor,
It has column lines to which input signals a to c are respectively applied, and a diode is connected between the row line and the column line to the "H" bit. In this embodiment, when the input signal a is "H", a code signal having the largest binary value is generated, and when the input signal c is "H", a code signal having the smallest value is generated. .

The code signal output from the matrix circuit 7 is sent to a comparator 8 and compared with the contents of a counter 9. When the two contents match, a limit signal of "H" is output, and as will be described later, the photographing lens 10 is restricted from exceeding the limit position.

As is well known, the distance measuring device 11 includes a photographing lens 10.
scan the subject optically or electrically in conjunction with
Outputs an "H" AF signal when the subject is in focus. The output signals of this distance measuring device 11 and the comparator 8 are input to an OR circuit 12. The output signal of this OR circuit 12 is
3, and when the coil 15 is energized, the stopper 1
Release the adsorption of 6. When the combination magnet 14 is released from adsorption, the stopper 16 is moved to the left by the spring 17, and the stopper 16 is moved to the left by the spring 17.
0 to prevent this rotation.

The gear 20 is connected to the motor 2 via a drive gear 22 fixed to the rotating shaft of the motor 21 and an intermediate gear 23.
Rotated by 1. The motor 21 rotates in reverse after photographing, rotates the gear 20 in reverse until the lever 20a hits the pin 24, and presses the release button (not shown).
Press to start normal rotation. The rotation of the gear 20 is transmitted to the gear 26, and moves the lens barrel 27 holding the photographic lens 10 from the short distance position toward the limit position.

The rotation of the intermediate gear 23 is transmitted to the disk 30. This disk 30 has slits 30a formed at regular intervals, and passage through the slits 30a is detected by a light source 31 and a light receiving section 32 placed before and after the slits 30a. The output signal of this light receiving section 32 is
It is sent to counter 9 and counted there.

Next, its operation will be explained. The subject brightness information measured by the photometry circuit 1 is sent to the comparators 3 and 4.
and is sent to the program shutter control circuit 5.
Depending on the subject brightness, any one of signals a to c
becomes "H" and controls the matrix circuit 7. This matrix circuit 7 outputs any one of three types of code signals according to the signals a to c.

When the release button is pressed, the motor 21 rotates,
The photographic lens 10 is moved from a close position to an infinite position. During this movement, when an AF signal is output from the range finder 11, the stopper 16 moves forward to prevent the gear 20 from rotating, and the photographing lens 10
position.

Since the rotary plate 30 rotates while the photographic lens 10 is moving, pulses are output from the light receiving section 32 and counted by the counter 9. When the outputs of the counter 9 and the matrix circuit 7 match, the comparator 8 outputs a limit signal of "H". Therefore, if the subject is located further away than the distance corresponding to the limit position, or if distance measurement is not possible, the limit signal is generated before the AF signal is output, so the shooting lens 1
0 is positioned at the limit position. This limit position is set at a position where the focus is approximately at the hyperfocal distance, and changes in three stages depending on the signals a to c.

After the focus adjustment described above, the program shutter control circuit 5 is activated to control exposure according to the program diagram shown in FIG. After photographing, the motor 21 starts rotating in reverse, and the lever 20a moves to the pin 24.
Return the gear 20 to the position where it hits. This results in
The photographic lens 10 is returned to the short distance position, and then the counter 9 is reset.

FIG. 2 shows a program diagram of the program shutter. When the light value LV is less than 10, the aperture is
It is fixed at f/2.8 and only the shutter speed changes.
When the light value LV is 10 or higher, both the aperture and shutter speed change.

FIG. 3 shows the relationship between the limit position and the light value. For LV11.5 and below, the limit position is set so that the focus is at 8.5m, which is the hyperfocal distance at F2.8. When using a photographic lens with a focal length of f38mm and a circle of least confusion of 0.06mm,
Below LV10, the periapsis is approximately 4.2m, and from LV10
11.5, the periapsis changes from about 4.2 m to about 3.4 m.
On the other hand, since the far point is at infinity, objects within the range between the near point and infinity can be clearly photographed.

When the light value is between LV11.5 and LV14.5, the limit position is set so that the focus is at 6.0 m, which is the hyperfocal distance when the aperture is set to F4. In this case, the periapsis varies between about 3 m and about 2 m.

For light values of LV 14.5 and above, the limit position is set so that the aperture is focused at a hyperfocal distance of 3.2 m at F8.

Straight line 35 shown by a dashed line indicates the limit position.
This shows the change in periapsis due to the aperture when the distance is fixed at 8.5m. As can be seen from a comparison with this straight line 35, in the present invention, the near point spreads toward the short distance side, so a clear image can be captured over a wider range.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an outline of the present invention. FIG. 2 is a program diagram. FIG. 3 is a graph showing the relationship between light value and limit position. 10... Photographing lens, 14... Combination magnet, 16... Stopper, 21... Motor, 30... Rotating plate, 30a... Slit, 3
1... Light source, 32... Light receiving section.

Claims (1)

[Claims] 1 When the subject brightness is below the first level, the aperture is kept constant and only the shutter speed changes;
A program shutter that changes both the aperture and shutter speed to control the exposure above this level;
a distance measuring device that detects the photographing distance to the subject; a photographing lens that moves from a short distance position toward a limit position at the time of release;
Below the first level, the limit position is the position where the focus is at the hyperfocal distance corresponding to the certain aperture, and above the first level, the subject brightness area is divided into a plurality of groups, one for each group. A limiter that sets the limit position to a position in focus at a determined hyperfocal distance, and means for positioning the photographing lens between the short distance position and the limit position based on a signal from the distance measuring device. An auto focus camera featuring